how do I plot temperature contours on a PV diagram?

I have a set of values of pressures(p1) and two sets of values for specific volumes (vapour(v1) & liquid(l1)) plotting these sets (v1,p1) & (l1,v1) in a LOG scale on both axes gave me a parabola looking cuve. Now I’m trying to plot two isotherms at two specific temperatures but I’m unsure how to go about it.

Any help would he appreciated, it has me really confused :(

Answer 1

[Star Strider]

Try this example —

Tv1 = linspace(273, 323, 10);
Tv2 = linspace(323, 373, 10);
Vv1 = linspace(150, 200, 10);
[T1m,V1m] = ndgrid(Tv1,Vv1);
[T2m,V1m] = ndgrid(Tv2,Vv1);
R = 0.2871;
m = 5;
% p1 = 7.8378;
% V1 = 50;

p = @(T,V) m*R*T./V;

figure
surf(T1m, V1m, p(T1m,V1m))
hold on
surf(T2m, V1m, p(T2m,V1m))
hold off
grid on
xlabel('T')
ylabel('V')
zlabel('p')
view(90,0)

Here ‘Tv1’ and ‘Tv2’ are temperature vectors, and ‘Vv1’ is a volume vector (note that they do not all have to be the same lengths because of the ndgrid calls that create matrices from the vectors). The ‘P’ anonymous function returns the pressure for values of temperature and volume. Use your own ranges for pressure, volume, and temperature. The view call is optional.

Experiment to get the result you want.